Speaker
Rachel Titus
(NSCL/MSU)
Description
Sensitivity studies of the late stages of stellar core collapse with respect to electron-capture rates indicate the importance of a region of nuclei near the N=50 shell closure, just above doubly magic 78Ni. In the present work, it has been demonstrated that uncertainties in key characteristics of the evolution, such as the lepton fraction, electron fraction, entropy, stellar density, and in-fall velocity are about 50% due to uncertainties in the electron-capture rates on nuclei in this region, although thousands of nuclei are included in the simulations. The present electron-capture rate estimates used for the nuclei in this region of interest are primarily based on a simple approximation, and it is shown that the estimated rates are likely overestimated by an order of magnitude or more. More accurate microscopic theoretical models are required to obtain Gamow-Teller strength distributions, upon which electron-capture rates are based. The development of these models and the benchmarking of such calculations rely on data from charge-exchange experiments at intermediate energies. An experimental campaign to study Gamow-Teller strength distributions in nuclei at and near N=50, including 86Kr and 88Sr, with the (t,3He) reaction at NSCL is underway and preliminary results, and their effects on future astrophysical work, will be presented.
Primary author
Rachel Titus
(NSCL/MSU)
Co-authors
B. Alex Brown
(NSCL/MSU)
Bingshui Gao
(NSCL/MSU)
Chris Sullivan
(NSCL/MSU)
Remco G. T. Zegers
(NSCL/MSU)
